Sudden restart of module

in the last two weeks i had this problem appr. 4 times:
the er-301 reboots in the middle of a working patch without warning, eg display gets dark and the module restarts, as if i accidentally pulled the power. there’s no power problem in the case, 100% sure about that.
i’m not quite sure if the incidents where this happened were similar, but i think more than 2 times i left the case running for quite a while (2 hours appr.) and didn’t touch the er301, when i then touched the big knob this abrupt reboot occured, as if i woke up the module, but it needed a fresh start…obviously the er301 patch was gone. what can i do to further test this behavior and find out what the problem might be?

Did you check the troubleshooting section on the wiki?

yes, but as already stated above i have more than enough power for the case:

12 V / 2000 mA
-12 V / 1200 mA
5 V / 4000 mA


hm, sorry, i only now saw this thread where a user had a similar problem:

i try to switch the 5v to reg tomorrow and will report back.
however this problem is new but power, case and module in it is not, so everything worked perfectly until now and the doepfer psu3 has enough on the 5v…

Should only use the 5V power option if absolutely necessary, apparently it’s always better to use the REG mode.

Good luck!!

Yes please report back in if the problem continues! @miminashi had a similar problem (a reproducible reboot when touching the knob after statically charging his body up) which seemed to be solved by grounding the encoder case. Particularly, try and see if you can make the problem reproducible by shuffling around on a carpet and then touching the ER-301’s knob.

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haha, that must be it, i am in a studio with a carpet floor and i have constant little shocks!!
ok, how do i ground the encoder case? actually, what do you mean by that, the case itself is grounded…

I also had this problem - my 301 would reboot randomly when touching the knob. I wear socks in a carpeted studio and my short haired dog sleeps under a polyester blanket nearby. There is a lot of static.

However, the problem turned out to be caused by the power cable being slightly loose at the 301 end. I think it must have wobbled loose when moving my case around. So check that first!

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since I had the same problem i’ll post a pm i had with Brian here
which contains a description of the problem as well as
Brian’s how-to…

@odevices: maybe it would be also a good idea to add
some similar information to the troubleshooting section in the wiki.
there’s already a similar issue which should be demarcated somehow.

  • rebooting after touching “the knob”
  • rebooting spontaniously, i.e. without any user interference…

here’s the info via pm:


some days ago I noticed the following behaviour:
whenever i get electrostatically charged by sliding my shoes on the floor
or when i take off a fleece shirt and then touch the knob the er-301 will reboot.

it does not happen when i touch the jacks or the switches of the er-301
it does not happen when i touch other modules
i tried 3 different PSUs (4ms row power 40, synthrotek super blue, tiptop mantis case)
i tried different power outlets in the appartment
i tried 5V from bus
do you have any idea why this is happening?

---------Brian’s reply:

It looks like you are sending a static discharge down the encoder shaft.

Are you handy enough to try grounding the encoder case to see if the problem goes away? The goal is to place a metal conductor from the indicated GND pin to the encoder housing.


I recommend some solid core wire that is easily bent to a desired shape. You can solder one end to the indicated GND pin and then bend the other end around to glue or tape to a convenient place on the encoder housing. Do not try to solder to the encoder housing.

that’s it!
thanks so far…

(i did not solder the resistor leg to the ground pin, just
spanned it in there and taped the other end to the panel
so it would have enough tension to make contact between pin and
encoder housing.)

i guess soldering to the encoder housing would need too much
heat that would endager the encoder and/or other connected

is the glue method your recommended permanent fix?
is there any chance that heating up that ground pin with the soldering iron
would fix a possible bad solder joint between the encoder board and that header?

------Brian’s reply

is the glue method your recommended permanent fix?


is there any chance that heating up that ground pin with the soldering iron would fix a possible bad solder joint between the encoder board and that header?

No. For some reason, the encoder manufacturer decided to not connect the encoder case to the ground pin.

ok then, i will go for glue :crazy_face:


thanks guys for your answers! quite relieved to hear that i’m not alone with this!
and thanks @mopoco for posting the picture and conversation with brian, i will try to attach a wire to the gnd pin and encoder housing!

this whole thing brings up the general question if static electricity could damage modules? i know for example that mungo modules come in a antistatic bag and that jon always writes that static electricity could damage the module. if you touch the pcb then i’m sure this can be problematic, but the panel side of the module? does anybody know a bit more about this subject? or maybe can someone explain, what happens on the er301 with this static electricity and why touching the knob leads to a prompt reboot?

Thank you @mopoco for posting the discussion we had.

I should add that this procedure has not been verified on my end because I haven’t been able to reproduce the behavior. It could be that once I am able to reproduce the reboot that I can find a simpler fix. So far I have not been able to produce any static electricity on my body at all. I believe this is why:

Humidity in Tokyo almost never falls below 50%:

So it is not likely that I will be able to reproduce the conditions here too. So I’m kind of looking for an artificial (and safe) method to produce static electricity charges.

As for why it is happening, I actually can’t see a clear reason why this should be happening. My top hypothesis is if you open up the encoder and look inside, there is a 3.3V trace that is running quite close to the edge of the board where the metal housing abuts.

Still its just guesswork until I can setup a proper verification test.

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I’ve managed to mess up my Synthesis Technology E350 twice because of static electricity (or at least that’s what I think is the problem). Seems that static electricity erased or corrupted a chip. Paul Schreiber was an angel and repaired/replaced it for me free of charge the first time. The second time it happened I didn’t have the heart to bother him again. Norway during winter is cold and fairly dry, so static electricity problems is common. I need to start taking precautions like touching something grounded before fiddling around with the modular.

so i tried to replicate this reboot problem with extensive walking around an all carpet studio and rubbing myself awkwardly against stuff…but it didn’t happen today. so, again i’m lost, power issue it is not, static electricity test failed…what else could it be? i didn’t had a patch running today…so maybe it’s also related to cpu usage? well anyway, happy that nothing happened today but also not happy since no answer to the problem in sight.

Did you get a noticeable static discharge? I am able to reliably build up a little static charge by moving from my computer to my modular setup (e.g., to reinsert the SD card to load a new firmware), and my ER-301 would restart without fail if there was a noticeable spark. After grounding the encoder housing as @odevices has described, I can zap the encoder knob to my heart’s content without so much as a hiccup from the ER-301. It has completely solved the issue for me.

Given all of the potential variables, how does one achieve such a state of certainty? :dizzy_face:

faith, pure faith…but no i tested my power supply when i built it (well not me, a professional). i have an external doepfer psu3 and since i switched to that all my power problems went away, so that’s why i believe in it…aaand of course because this reboot problem only happened in this new carpet studio…so i still think it’s static electricity.

In about 5 hours of usage last night my ER-301 rebooted twice, and I believe both times it was when touching the encoder after a few minutes of not touching it.

I do frequently get static shocks in the winter, though I always discharge myself on furniture before touching my synths or computer. With my current case situation, my ER-301 is mounted in a spot that encourages standing up to reach it easily, so I probably built up just enough charge doing that to zap it a couple of times. (I have a new case which should be shipping soon and the ER-301 will be placed much more conveniently.)

I’ll take more care about static, and also look into grounding the encoder housing. And also try to get into the habit of quicksaving :laughing:

Known issue, for some folk, I have never experienced this, but me and electricity are very best friends and we allow each other a great deal of leniency; answer here…

The encoder on your unit should already be grounded. What is your case ground attached to?